Novel polymer-based composites with high dielectric constant and low dielectric loss were prepared by simply mixing polyvinylidene fluoride (PVDF) with semiconductor vanadium pentoxide (V2O5) filler. V2O5 nanobelts with diameter around 50 nm and length up to micrometer scale were uniformly distributed in PVDF matrix without serious aggregation. The PVDF/V2O5 composites show excellent dielectric properties. When the volume fraction of V2O5 is 0.15 and the frequency is 100 Hz, the dielectric constant of the composites can reach as high as 140 and the dielectric loss is 0.7. Both dielectric constant and dielectric loss of the composites show but sharp increase when the volume fraction of V2O5 is above 0.15. Furthermore, the dependences of the dielectric constant and dielectric loss on frequency were also studied. With the increase of frequency from 102 to 107 Hz, dielectric constant of the PVDF/V2O5 composites decreases, while the dielectric loss increases slightly. The results indicate that the PVDF/V2O5 composites are promising materials for capacitors.